title: Three dimensional, radiosteriometric analysis (RSA) of equine stifle kinematics and articular surface contact: a cadaveric study.
abstract: BACKGROUND
  Studies examining the effect of stifle joint angle on tibial rotation, adduction-abduction angle and articular contact area are lacking.
  
  
  OBJECTIVE
  To test the hypothesis that tibial rotation, adduction-abduction angle and articular contact area change with stifle joint angle.
  
  
  METHODS
  Descriptive study of normal kinematics and articular contact patterns of the equine stifle through the functional range of motion using 3 dimensional (3D) radiosteriometric analysis (RSA) and equine cadaver stifles.
  
  
  METHODS
  Multiple, radiopaque markers were embedded in the distal femur and proximal tibia and sequential, biplanar x-rays captured as the stifle was passively extended from 110° to full extension. Computer-programmed RSA was used to determine changes in abduction-adduction and internal-external rotation angles of the tibia during stifle extension as well as articular contact patterns (total area and areas of high contact) through the range of motion.
  
  
  RESULTS
  The tibia rotated externally (P < 0.001) as the stifle was extended. Tibial abduction occurred from 110-135° of extension (P < 0.001) and tibial adduction occurred from 135° through full extension (P = 0.009). The centre of joint contact moved cranially on both tibial condyles during extension with the lateral moving a greater distance than the medial (P = 0.003). Articular contact area decreased (P = 0.001) in the medial compartment but not in the lateral compartment (P = 0.285) as the stifle was extended. The area of highest joint contact increased on the lateral tibial condyle (P < 0.001) with extension but decreased (P = 0.001) on the medial tibial condyle.
  
  
  CONCLUSIONS
  Significant changes occur in tibial rotation, adduction-abduction angle and articular contact area of the equine stifle through the functional range of motion. Understanding the normal kinematics of the equine stifle and the relationship between joint positions and articular contact areas may provide important insight into the aetiology and location of common stifle joint pathologies (articular cartilage and meniscal lesions).
authors.affiliation: Laboratory for Comparative Orthopaedic Research, Michigan State University, USA.
authors.forename: S E
authors.initials: SE
authors.lastname: Halley
authors.forename: M J
authors.initials: MJ
authors.lastname: Bey
authors.forename: J A
authors.initials: JA
authors.lastname: Haladik
authors.forename: M
authors.initials: M
authors.lastname: Lavagnino
authors.forename: S P
authors.initials: SP
authors.lastname: Arnoczky
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002102:Cadaver; D006736:Horses / Q000033:anatomy & histology / Q000502:physiology*; D059869:Radiostereometric Analysis / Q000662:veterinary*; D013264:Stifle / Q000502:physiology*
keywords: 3D; abduction-adduction; horse; joint contact; rotation; stifle